1. Technical Field
The present disclosure generally relates to a composite optical film and a backlight module using the same, and more specifically to a composite optical film integrating a brightness enhancement film and a diffuser, and a backlight module using the same.
2. Description of the Prior Art
Since Liquid crystal displays (LCD) have the advantages of as slimness, lightness, high brightness, high contrast ratio and low power, they have replaced cathode ray tube displays and became main products in the market. However, LCD panels are passive light-emitting planar display devices, so a backlight module is therefore necessary on the back side of each of the LCD panels to provide light for display.
Please refer to FIG. 1, which schematically depicts a cross-sectional view of a conventional backlight module. As shown in FIG. 1, a conventional backlight module 10 is composed of a light guide plate 12, a plurality of optical films disposed on the light guide plate 12, and a light source 16 disposed at one side of the light guide plate 12. The optical films 14a, 14b, 14c, 14d may include a lower diffuser 14a, a lower brightness enhancement plate 14b, an upper brightness enhancement plate 14c and an upper diffuser 14d sequentially disposed on the light guide plate 12. Light generated by the light source 16 emits into the light guide plate 12 from a sidewall of the light guide plate 12 that is then guided to emit upwards. Thereafter, the light emitting out of the light guide plate 12 passes through the lower diffuser 14a, thereby enabling the light to diffuse uniformly and to be concentrated into a light beam. Then, the light emitting out of the lower diffuser 14a is focused by the lower brightness enhancement plate 14b and the upper brightness enhancement plate 14c and equalized by the upper diffuser 14d, so as to have a luminance-uniform surface light source.
Therefore, the conventional backlight module 10 needs a plurality of optical films 14a, 14b, 14c, 14d to have an ideal back light. Assembling the plurality of optical films 14a, 14b, 14c, 14d will increase the material costs, the assembling process steps, and the assembling time, thereby increasing the processing costs. Besides, optical films 14a, 14b, 14c, 14d may easily rub against each other, leading to scratches or damages that will affect the light emitting brightness of the conventional backlight module 10 and reduce processing yields. Moreover, each of the optical films 14a, 14b, 14c, 14d must have a large enough thickness to keep its physical properties, thereby resulting in limiting the thickness of the conventional backlight module 10.
Therefore, it is an important issue in the industry to decrease the numbers of the optical films in order to reduce the processing costs and reduce the thickness of the backlight module.